Absorbent articles for personal hygiene such as disposable diapers, feminine protection pads and adult incontinence undergarments, are designed to absorb and contain body exudates, in particular but not limited to urine. These absorbent articles usually comprise several layers having different functions, for example a topsheet, a backsheet and in-between an absorbent core, among other layers. The absorbent core's function is to absorb and retain the exudates for a prolonged amount of time, for example overnight for a diaper, minimize re-wet to keep the wearer dry and avoid soiling of clothes or bed sheets.
Absorbent cores can expand several times their initial volumes when wet. It is desirable that the cores in this expanded state maintain their structural integrity and do not break or burst even when submitted to a shock such as a child sitting heavily on his diaper. It is also desirable that absorbent cores should be thin (at least when dry) and require as little material as possible for costs and environmental reasons.
The majority of currently marketed absorbent cores for diapers however comprise as absorbent material a blend of comminuted wood pulp with superabsorbent polymer particles (SAP), also called absorbent gelling materials (AGM), see for example U.S. Pat. No. 5,151,092 (Buell). Absorbent articles having a core consisting of essentially SAP as absorbent material (so called “airfelt-free” cores) have also been proposed but are less common than traditional mixed cores (see e.g. WO2008/155699, Hundorf).
US2008/0312621 and US2008/0312622 (Hundorf) describe a disposable absorbent article comprising a chassis including a topsheet and a backsheet, a substantially cellulose free absorbent core located between the topsheet and the backsheet and having a wearer facing side oriented toward a wearer when the article is being worn and an opposed garment facing side, and a liquid acquisition system comprising chemically cross-linked cellulosic fibers disposed between the liquid permeable topsheet and the wearer facing side of the absorbent core. The liquid acquisition system may comprise a nonwoven as an upper acquisition layer and a lower acquisition layer which may comprise chemically cross-linked cellulose fibers. In such a design the lower acquisition layer contacts the upper substrate of the cellulose free absorbent core. A typical process to make such a liquid acquisition system is airlaying the unbound chemically cross-linked cellulose fibers onto the upper acquisition layer nonwoven: in this case, the upper acquisition layer nonwoven always fully covers the lower acquisition layer comprising the chemically cross-linked cellulose fibers.
However it may be desirable to use an upper acquisition layer nonwoven which is shorter or narrower or in an offset position relative to the lower acquisition layer, for instance for cost savings or performance optimization. Additionally if an apertured topsheet is used, it is desired to limit the amount of unbound fibers that could reach the wearer skin through the apertures of the apertured topsheet. Finally the lower acquisition layer may tend to retain liquid due to the hydrophilicity and the pore size of the chemically cross-linked cellulose fibers, whereas the presence of a core cover between the lower acquisition layer and the superabsorbent particles may make it more difficult for the superabsorbent polymers to dewater the lower acquisition layer.
The present inventors have now found a new core structure for absorbent articles, which may address the above described limitations, while delivering a very good fluid handling performance.